When migrating from a legacy environment to a multi-tenant cloud platform like Salesforce, Data volume and processing volume represent the most critical technical constraints. Legacy systems often operate without the strict governor limits found in Salesforce, meaning they may push large datasets or high-frequency updates that could easily overwhelm standard Salesforce APIs.

An integration architect must evaluate these volumes to determine the appropriate integration pattern:

Pattern Selection: If the daily volume involves millions of records, the architect must recommend the Bulk API rather than standard REST or SOAP APIs to avoid hitting daily API limits.

Synchronous vs. Asynchronous: High processing volumes often necessitate asynchronous patterns (such as Fire-and-Forget or Batch) to prevent user-interface lag and "Concurrent Request Limit" errors.

Data Virtualization: If the legacy data volume is massive but only needs to be viewed occasionally, the architect might consider Salesforce Connect to avoid consuming expensive internal data storage.

While reporting (Option A) and multi-currency (Option C) are important functional requirements, they do not fundamentally dictate the technical "plumbing" or scalability of the integration architecture. By prioritizing the analysis of volume and processing needs, the architect ensures the new modernization effort is stable, performant, and capable of scaling as the business grows within the bounds of the Salesforce platform.